US20160338770A1 - Woven foldable catheter - Google Patents

Abstract

Apparatus, consisting of a catheter having a distal end and a predefined outer diameter. The apparatus also has a plurality of elastic filaments, each filament having at least one electrode fixed thereto and having two ends fixed within the catheter distal end to hold the filament as a loop. The loop intertwines with one or more other loops of the other filaments so that the plurality of the filaments forms an open lattice, which expands when uncompressed to a lattice diameter at least 5 times greater than the outer diameter of the catheter.

Description

FIELD OF THE INVENTION
• The present invention relates generally to catheters, and specifically to formation of the distal end of a catheter.
BACKGROUND OF THE INVENTION
• During a medical procedure on the heart, such as an ablation, the energy for the ablation may be radio-frequency energy that is injected into the heart via electrodes contacting the heart. The electrodes, or other electrodes, may also be used to monitor the condition of the heart, by acquiring signals from the heart as it beats. Present day ablation procedures typically use a relatively large number of electrodes simultaneously, and such electrodes may be provided in specially designed catheters, such as basket, pent-array or lasso catheters.
SUMMARY OF THE INVENTION
• An embodiment of the present invention provides apparatus, including:
• a catheter having a distal end and a predefined outer diameter; and
• a plurality of elastic filaments, each filament having at least one electrode fixed thereto and having two ends fixed within the catheter distal end to hold the filament as a loop. The loop intertwines with one or more other loops of the other filaments so that the plurality of the filaments forms an open lattice, which expands when uncompressed to a lattice diameter at least five times greater than the outer diameter of the catheter.
• Typically, the open lattice compresses to fit within a cylinder having a diameter equal to the predefined outer diameter of the catheter.
• In a disclosed embodiment the open lattice when uncompressed is sized to be enclosed by a virtual spherical envelope. Alternatively, the open lattice when uncompressed is sized to be enclosed by a virtual open conical envelope.
• In a further disclosed embodiment the open lattice when uncompressed has open spaces between the intertwined filaments, and a ratio of a first total area defined by the open spaces and a second total area defined by the filaments is at least 5:1.
• In a yet further disclosed embodiment each elastic filament consists of a tube having a lumen, and the at least one electrode is attached to a conductive wire traversing the lumen.
• In an alternative embodiment the lattice diameter includes a largest distance between selected sections of the plurality of elastic filaments.
• There is further provided, according to an embodiment of the present invention, a method, including:
• providing a catheter with a distal end and a predefined outer diameter; and
• fixing a plurality of elastic filaments within the catheter distal end, each filament having at least one electrode fixed thereto and having two ends fixed within the catheter distal end to hold the filament as a loop, wherein the loop intertwines with one or more other loops of the other filaments so that the plurality of the filaments forms an open lattice, and wherein the open lattice expands when uncompressed to a lattice diameter at least five times greater than the outer diameter of the catheter.
• The present disclosure will be more fully understood from the following detailed description of the embodiments thereof, taken together with the drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a schematic illustration of a minimally invasive medical system, according to an embodiment of the present invention;
• FIGS. 2, 3, 4, 5 and 6 are different schematic views of a distal end of a probe, according to embodiments of the present invention; and
• FIGS. 7 and 8 are two views illustrating an uncompressed open lattice, according to an alternative embodiment of the present invention.
DETAILED DESCRIPTION OF EMBODIMENTSOverview
• Many catheters, such as pent-array, lasso, or basket catheters, may push the heart wall when attempting to conform to the shape of the wall during a medical procedure, such as an ablation, performed on the wall. In addition, these types of catheters have relatively sharp regions (the ends of the splines in the case of a pent-array or lasso catheter; the distal end of the basket in the case of a basket catheter). For catheters with open ended constructions, such as the pent-array or lasso catheters, it is difficult to maintain their shape during operation. (In the pent-array catheter the ends tend to overlap; in the lasso catheter the lasso end tends to entangle with the remainder of the lasso, and relatively large forces are required to counteract these effects.) For all these types of catheters the combination of the required force and sharp regions may have undesired results during use of the catheters in medical procedures such as those referred to above.
• Embodiments of the present invention overcome both of the problems. A plurality of elastic filaments are attached to the distal end of a catheter, each filament having fixed to it at least one electrode. The two ends of each filament are fixed within the catheter, typically within the distal tip of the distal end, so that each filament forms a loop with no sharp regions. The loops formed by the filaments are configured to intertwine in a woven manner with each other, so that the plurality of the filaments form an open lattice. The elasticity of the filaments allows the open lattice to exist in a compressed or in an uncompressed form.
• In the compressed form, the catheter with its compressed open lattice may be inserted into a sheath that guides the distal end of the catheter to a desired location, typically in the heart during a procedure being performed on the heart. At the desired location the compressed open lattice exits the sheath, and decompresses to form an uncompressed open lattice.
• The uncompressed open lattice is relatively large, having a lattice diameter at least five times larger than the outer diameter of the catheter distal end, so that the electrodes of the lattice are able to contact the heart wall. However, the elasticity of the filaments, and their lack of sharp edges, prevents trauma to the heart.
• By having the loops of the filaments intertwine with, and cross, each other, in the woven manner referred to above, the uncompressed open lattice formed by the loops is able to maintain its shape.
System Description
• Reference is now made toFIG. 1, which is a schematic illustration of a minimally invasivemedical system20, according to an embodiment of the present invention.System20 is typically used during a medical procedure on a body organ, and in the description herein the body organ, by way of example, is assumed to comprise the heart, wherein the system is applied to sample, and typically record and analyze, intra-cardiac electrocardiogram (ECG) signals. However, it will be understood thatsystem20 may be applied to sample other signals from other body organs.
• The following description assumes thatsystem20 senses intra-cardiac ECG signals from aheart22, using aprobe24.Probe24 typically comprises a catheter, and is herein also referred to ascatheter24. Adistal end26 of the probe is inserted into the body of asubject30.Distal end26 of the probe, described in more detail below, comprises a plurality ofelectrodes28 which sense the ECG signals. Prior to insertion of the probe intoheart22, asheath34 may be inserted into the subject until the distal end of the sheath is in a desired location. Once the distal end of the sheath has been correctly positioned,probe24 may be inserted intosheath34 untildistal end26 of the probe exits from the distal end of the sheath. In the description herein auser32, typically a medical professional, is assumed to insert the sheath and the probe.
• System20 may be controlled by asystem processor40, comprising aprocessing unit42 communicating with anECG module44.Processor40 may be mounted in aconsole50, which comprises operating controls which typically include a pointing device such as a mouse or trackball. Console50 also connects to other elements ofsystem20, such as aproximal end52 ofcatheter24. Professional32 uses the pointing device to interact with the processor, which, as described below, may be used to present results produced bysystem20 to the professional on ascreen54.
• The screen displays results of analysis and processing of ECG signals byECG module44. Typically, the resultant ECG signals are presented onscreen54 in the form of a potential vs. time graph, and a schematic example60 of such a graph is illustrated inFIG. 1. However, the resultant ECG signals may also be used byprocessor40 to derive other results associated with the ECG signals, such as a local activation time (LAT). These results are typically presented onscreen54 in the form of a three-dimensional (3D)map64 of the internal surface ofheart22.
• Processor40 uses software stored in a memory of the processor to operatesystem20. The software may be downloaded toprocessor40 in electronic form, over a network, for example, or it may, alternatively or additionally, be provided and/or stored on non-transitory tangible media, such as magnetic, optical, or electronic memory.
• Processor40 typically comprises other modules, such as a probe tracking module and an ablation module that provides regulated power to one ormore electrodes28, or to one or more other electrodes in the distal end. For simplicity, such modules are not shown inFIG. 1. The Carto® system produced by Biosense Webster, of Diamond Bar, Calif., uses such modules.
• FIGS. 2, 3, 4, 5 and 6 are different schematic views ofdistal end26 ofprobe24, according to embodiments of the present invention.FIG. 2 illustrates the probe distal end prior to exiting, or after reentering, the distal end ofsheath34.FIG. 3 illustrates probedistal end26 when it is exiting or reenteringsheath34.FIGS. 4 and 5 illustrate probedistal end26 when it has completely exitedsheath34, in two different views.FIG. 6 schematically illustrates, in cross-section, a single loop attached todistal end26.
• Distal end26 comprises a plurality of flexibleelastic filaments100, eachfilament100 being typically formed from a conductive element such as a nitinol tube. As is illustrated inFIG. 6, each filament has two ends,102,104, both of which are fixed todistal end26 ofcatheter24, typically at atip110 of the distal end, so that each filament forms a loop.Distal end26 of the catheter has an outer diameter d. Iffilaments100 are conducting, for example if they are formed from nitinol, they are typically covered with an insulating material. Alternatively,filaments100 may be formed from insulating material.
• Eachfilament100 has at least oneelectrode28 fixed to the filament. If the filaments are in the form of a tube, conductingwires116, insulated iffilament100 is conductive, may be attached through holes in the filaments to the electrodes, and the wires may be fed through and traverse a lumen of the tube (as illustrated inFIG. 6), viadistal end26 andproximal end52 ofcatheter24, to console50. Signals acquired by the electrodes may thus be analyzed by processor49. Alternatively, iffilaments100 are not tubular,wires116 may be cemented to the outside of the filaments.
• The filaments are fixed todistal end26 so that the loops formed by each of the filaments intertwine to form an open lattice. The loops of the open lattice are arranged in a woven manner so that they interlace and cross each other, and so that they are able to slide against each other. Because of the elasticity of its constituent filaments, the open lattice may be in a compressed form as a compressedopen lattice118, illustrated inFIG. 2. The open lattice of the filaments may also be in an uncompressed form as an uncompressedopen lattice120. Two views ofopen lattice120 are provided inFIG. 4 andFIG. 5. When the filaments are fixed to the distal end, they are arranged so that uncompressedopen lattice120 has a predefined shape, which is sized to fit within a virtual envelope. In the case ofopen lattice120, it has a spherical shape and is sized so that it can be enclosed by a sphericalvirtual envelope124.
• Uncompressedopen lattice120 is formed of intertwinedfilaments100, between which there are open spaces130 (FIGS. 4 and 5). In one embodiment, a ratio of a total area of the open spaces to a total area offilaments100 is at least 20:1, where both areas are defined as the area produced by projection, from a center of the virtual envelope, of the open spaces and of the filaments onto the envelope. In other embodiments the ratio may be at least 5:1.
• Uncompressedopen lattice120 also has a lattice diameter D, which is the largest distance between any two sections offilaments100 forming the lattice. In some embodiments lattice diameter D may alternatively be considered as the largest distance between points on the virtual envelope sized to enclose the uncompressed open lattice, so that in the case of sphericalvirtual envelope124, lattice diameter D corresponds to the diameter ofenvelope124. Lattice diameter D is at least 5 times greater than outer diameter d ofdistal end26 of the catheter, and is typically 20 times or more greater than d.
• As stated above, in a typical cardiacprocedure using system20,sheath34 is initially inserted so that the distal end of the sheath is in a desired location with respect toheart22.Filaments100 are compressed so that they form compressedopen lattice118, and so that the filaments are able to entersheath34. In some embodiments compressedopen lattice118 is small enough to fit into a cylinder having the same diameter d as the outer diameter of thedistal end26. In it's the lattice compressed formdistal end26 and its attached filaments may then be pushed into the sheath until it reaches the end of the sheath.FIG. 2 schematically illustratesdistal end26 with its attachedfilaments100 withinsheath34, andFIG. 3 schematically illustrates the distal end and the filaments as the latter exit from the sheath.
• After exiting from the sheath,filaments100 decompress so that the filaments, in their uncompressed state, form uncompressedopen lattice120. At the termination of the procedure,distal end26 may be pulled in a proximal direction, so thatfilaments100 are compressed by the sheath and reenter the sheath as compressedopen lattice118.
• FIGS. 7 and 8 are two views illustrating an uncompressedopen lattice220, according to an alternative embodiment of the present invention. Apart from the differences described below, uncompressedopen lattice220 is generally similar to uncompressed open lattice120 (FIGS. 4 and 5) and elements indicated by the same reference numerals in both lattices and in both sets of figures are generally similar in construction and in operation. Thuslattice220 is formed from a plurality of intertwinedfilaments100, each of the filaments having at least oneelectrode28. Each of the filaments is fixed by respective ends of the filaments todistal tip110, so that each filament is in the form of a loop. There arespaces130 betweenintertwined filaments100.
• However, in contrast to uncompressedopen lattice120, the predefined shape of uncompressedopen lattice220 is an open glove or cone, so thatlattice220 is sized to be enclosed by a conicalvirtual envelope224. As forlattice120,lattice220 has a lattice diameter D that is equal to the largest distance between any two sections offilaments100 forminglattice220. Alternatively, the lattice diameter may be considered as the largest distance between points onenvelope224. As forlattice120,filaments100 of uncompressedopen lattice220 may be compressed to form a compressed open lattice which is able to entersheath34.
• It will be understood that embodiments of the present invention comprise other shapes, apart from the specific shapes described above with reference to uncompressedopen lattices120 and220. For example, other uncompressed open lattices, formed offilaments100 fixed todistal tip110, all of which lattices may compress to fit withinsheath24, are in the form of an ellipsoid or a paraboloid. All such open lattices are assumed to be comprised within the scope of the present invention.
• It will thus be appreciated that the embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.

Claims (14)

We claim:

1. Apparatus, comprising:

a catheter having a distal end and a predefined outer diameter; and

a plurality of elastic filaments, each filament having at least one electrode fixed thereto and having two ends fixed within the catheter distal end to hold the filament as a loop, which intertwines with one or more other loops of the other filaments so that the plurality of the filaments forms an open lattice, which expands when uncompressed to a lattice diameter at least five times greater than the outer diameter of the catheter.

2. The apparatus according toclaim 1, wherein the open lattice compresses to fit within a cylinder having a diameter equal to the predefined outer diameter of the catheter.

3. The apparatus according toclaim 1, wherein the open lattice when uncompressed is sized to be enclosed by a virtual spherical envelope.

4. The apparatus according toclaim 1, wherein the open lattice when uncompressed is sized to be enclosed by a virtual open conical envelope.

5. The apparatus according toclaim 1, wherein the open lattice when uncompressed comprises open spaces between the intertwined filaments, and wherein a ratio of a first total area defined by the open spaces and a second total area defined by the filaments is at least 5:1.

6. The apparatus according toclaim 1, wherein each elastic filament comprises a tube having a lumen, and wherein the at least one electrode is attached to a conductive wire traversing the lumen.

7. The apparatus according toclaim 1, wherein the lattice diameter comprises a largest distance between selected sections of the plurality of elastic filaments.

8. A method, comprising:

providing a catheter with a distal end and a predefined outer diameter; and

fixing a plurality of elastic filaments within the catheter distal end, each filament having at least one electrode fixed thereto and having two ends fixed within the catheter distal end to hold the filament as a loop, wherein the loop intertwines with one or more other loops of the other filaments so that the plurality of the filaments forms an open lattice, and wherein the open lattice expands when uncompressed to a lattice diameter at least five times greater than the outer diameter of the catheter.

9. The method according toclaim 8, wherein the open lattice compresses to fit within a cylinder having a diameter equal to the predefined outer diameter of the catheter.

10. The method according toclaim 8, wherein the open lattice when uncompressed is sized to be enclosed by a virtual spherical envelope.

11. The method according toclaim 8, wherein the open lattice when uncompressed is sized to be enclosed by a virtual open conical envelope.

12. The method according toclaim 8, wherein the open lattice when uncompressed comprises open spaces between the intertwined filaments, and wherein a ratio of a first total area defined by the open spaces and a second total area defined by the filaments is at least 5:1.

13. The method according toclaim 8, wherein each elastic filament comprises a tube having a lumen, and wherein the at least one electrode is attached to a conductive wire traversing the lumen.

14. The method according toclaim 8, wherein the lattice diameter comprises a largest distance between selected sections of the plurality of elastic filaments.

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